Lecture 23 Flashcards
How is predecidualization started?
In response to estrogen priming followed by actions of progesterone
Endometrial differentiation doesn’t require what major factor?
Embryo
Can predecidualization be induced?
In non-pregnant mice following mating or artificially induced decidualization (scartching cervix or infusing w/ progesterone-oil emulsion)
When does pre-decidualization of the uterine stroma occur?
During the menstrual cycle and continues of in presence of embryo
Why does decidualization occur?
- Lifespan of stromal cells is limited
- terminally differentiate to function as maternal part of the placenta
- Polyploidy might contribute to limited and specialized life (demise makes room for embryo, increased synthetic capacity -> increased transcription of genes)
What does decidual tissue make up?
Maternal Placenta - site of contact and communication between conceptus and mother, limits invasion into uterus, produces luteotropic hormones
What is artifical decidual tissue called?
Deciduoma
Where does human stroma decidualization occur?
Mesometrial site of implantation
How is stromal decidualization regulated?
Cyclin A,B/cdk1 during proliferation (mitosis)
What is the next steps after mitosis in decidualization?
Increase in p21 and concomitant downregulation of cyclin D3 and cdk4
Differentiation steps in decidualization:
- Cyclin D3 and cdk4 have a role in stromal cell proliferation
- Decidualization activates p21 which inhibits cdk4
- Consequently, switch from cdk4 to cdk6/P21: progression through G phase and induction of endocycle
What are the steps of early embryogenesis?
- 2nd wk, embryoblast differentiats into 2 germinal layers (epiblast and hypoblast)
- 3rd wk, epiblast undergoes differentiation fo the 3 embryonic germinal layers
What does the epiblast form?
Tissue of the embryo as well as the amniotic epithelium
What does the hypoblast form?
Umbilical vesicle
What is the process of differentiation of the 3 embryonic germinal layers?
- Appearance of the primitive streak
- Laterally immigrating cells sink down to form deep layers of the meso blast and endoblast
What is the primitive streak?
An accumulation of cells along the midline
What are the three parts of the mesoblast?
paraxial, intermediate and lateral plate mesoderm (trilaminar germ disk)
What is the process of differentiation of the early embryo?
Day 6 - Differentiation of the epiblast and hypoblast
Day 7.5 - Primordial amniotic cavity forms within epiblast, hypoblast growth and differentiates into parietal endoderm
Day 8 - Open roof of amniotic cavity formed, parietal endoderm development, extraembryonic mesoderm formation, beginning of yolk sac within parietal endoderm
Day 9 - More extraembryonic mesoderm, primary villi appears, Primary yolk sac completed
Day 14 - Primary yolk sac mostly degraded, secondary yolk sac formed, amniotic membrane differentiated, secondary villi developed, extraembryonic coelom developed, extraembryonic mesoderm differentiate into splanchnic mesoderm of yolk sac
What are the functions of the placenta?
- Gas transfer (lungs)
- Excretory functions, water balance and pH regulation (kidney)
- Catabolic and resorptive functions (gut)
- Synthetic and secretory functions (endocrine)
- Metabolic and secretory functions (liver)
- Hematopoiesis of the bone marrow
- Heat transfer of the skin
- Immunological functions
How are villi formation different in pigs vs. rodents/humans
diffuse structure vs. round cotyledons
Difference in cotyledons in rodents vs humans
Single cotyledon (discoid placenta) vs. multiple cotyledons consolidated into a clust that resembles a single disc
How is the structure of the trophoblast cell layer specific to rodents and primates?
Uterine epithelium (endometrium) is eroded away so that maternal blood comes into direct contact with the trophoblast surface (called hemochorial)
How doe rodents trophoblast layer differ from humans?
trichorial (2 syncytial layers and a mononuclear cell type layer) vs. single syncytial layer + an underlying trophoblast stem cell layer
Overview of implantation of human embryo:
- Trophoblast pentrates epithelium and invades the stroma
- Blastocyst sinks further into stroma and amnionic cavity appears
- Uterine tissue has grown over the implantation site (deciduoma response) and irregular spaces, blood sinusoids, have appeared in the syncytiotrophoblast
What are integrins?
A family of more than 20 different transmembrane receptors w/ non-covalently associated alpha and beta heterodimers
